If O-sensei made notes in his books this would be an important primary source of information, of course only related to the books in question. It would certainly illuminate as to his thinking.

Another question. The menkyo-kaiden in aiki bo-jutsu given to Hikitsuchi sensei.

This dates from the 1955 period where you assume O-sensei was most fully developed.

The text was presumably written by O-sensei, while the artist probably used O-sensei as a model for the illustrations.

Considering the time investment/cost of this scroll it would obviously have to be something O-sensei considered important.

The progression from ikkyo to gokyo which you describe in some way mirrors O-sensei's progression. The variable jo/spear exercise which he shows corresponding to the fourth and fifth levels. The 31 step jo kata would be an exercise on the second/third level.